1. Field of the Invention
The present invention relates to a method and apparatus for detecting foreign particles existing on the surface of a substrate.
2. Description of the Prior Art
The conventional foreign particle detecting apparatus is constructed, as disclosed in the U.S. Pat. No. 4,342,515, in a manner shown in FIG. 1. In this Figure, s-polarized laser beams 5, 6 from linearly polarized laser oscillators 3, 4 are irradiated to a foreign particle 2 on a wafer 1 sidewards along two directions, and a random polarized laser light 7 is scattered from the foreign particle 2. After the random polarized light 7 is focused by a condenser lens 8, only the s-polarized light of the condensed laser light is blocked by an analyzer 9; then, only a p-polarized light 10 is passed through a slit 11 for limiting the detection field and is detected by a photoelectric conversion device 12. On the other hand, the s-polarized light is scattered from an edge of a circuit pattern. Therefore, the presence of a foreign particle is recognized according to the output of the photoelectric conversion device 12.
In the conventional foreign particle detecting apparatus however, a wafer 1 being rotated must be fed along an axial direction of said wafer surface; hence, the foreign particle detecting speed is disadvantageously reduced.